Such a flight control indicator is more specifically adapted to an airplane, in particular a military transport airplane, which exhibits a low thrust/weight ratio and high inertia, and whose maneuvering times are relatively slow.
Although not exclusively, the present invention applies more particularly to low altitude flight. The expression low altitude flight is understood to mean flight along a flight trajectory (at low altitude) allowing an aircraft to follow as closely as possible the terrain overflown, in particular to avoid being pinpointed. Such a flight trajectory at low altitude is therefore situated at a predetermined terrain height, for example 500 feet (or 150 meters).
A low altitude flight therefore presupposes that one is flying as low as possible in valleys so as to benefit from effective masking with the aid of the surrounding relief, while still of course being in a position to be able to overfly the highest peaks that show up in front of the aircraft. When the aircraft is piloted manually by the pilot, that is to say without automatic pilot or flight director engaged, all the burden of low altitude flight control rests on the pilot.
In such a situation, the pilot generally has available only a ground anticollision system, of the GCAS type (GCAS standing for “Ground Collision Avoidance System”), to avoid a collision with the ground. This standard system provides an alarm when a maneuver does not make it possible to overfly the terrain in front of the aircraft, while maintaining defined flight conditions. This system uses theoretical climb models, established through a nominal aircraft, that is to say one which is not degraded. Thus, if the aircraft has suffered damage affecting its climb capabilities, the system provides erroneous information with respect to the current situation. This known system therefore provides no indication as to the actual maximum climb performance of the aircraft.
Consequently, no specific information (based on the current state of the aircraft) regarding the maximum capability of the aircraft to overfly a peak downstream in the direction of flight is available to the pilot. However, it is appreciated that knowledge of the maximum climb capability of the aircraft would allow the pilot to descend as low as possible in valleys until he reaches the limit for being able to climb back and negotiate the peak in front of him, which would increase the masking of the aircraft by the terrain.